1. Field of the Invention
The present invention relates to the convex bending or cambering of glass plates and to their tempering or hardening. It more particularly relates to the convex bending and hardening procedure in which the glass plates undergo convex bending, while being conveyed on a conveyor whose glass plate support members are arranged along a curved trajectory or path.
2. Background of the Related Art
A convex bending procedure, optionally extended by a thermal hardening, is described in French Patents No. 2 442,219 U.S. Pat. No. 4,540,426 and in European Patent No. 263 030. In these specifications, a description is given of conveyors with linear rollers, whose bearings are located along a curved path, which is descending or preferably rising, so as to give the glass plates raised to their convex bending temperature and which are therefore deformable under the effect of gravity, a simple curvature, i.e. a curvature in a single direction, or cylindrical curvature when they are travelling on these conveyors. A description is also given of conveyors having rollers or bent rods, whose bearings are, as above, arranged along a curved path, thus constituting for the glass plates heated to the convex bending temperature travelling thereon, a double curvature shaping bed, namely curvature both in the direction of travel of the glass plates as a result of the arrangement of the rollers or bent rods along the curved path, and a transverse curvature in the direction perpendicular to the travel direction, as a result of the bent form of the rollers or rods.
The aforementioned U.S. Pat. No. 4,540,426 also proposes a recovery of the glass plates at the upper end of the convex bending and hardening apparatus with a curved profile in the glass plate advance direction. This recovery is carried out by a swinging or tilting system in which each glass plate is engaged at the end of the convex bending and hardening operation, said system swinging or tilting under the effect of the overhang created by the weight of the glass plate and depositing said plate on a conveyor which does not have the inclined orientation of the end of the convex bending and hardening apparatus, but instead has a different orientation which can be substantially horizontal if desired. After tilting each glass plate onto the discharge conveyor, the tilting system freed from the overhang created by the glass plate returns by reverse tilting to its initial waiting position for the following glass plate.
This tilting system is satisfactory. However, it is only used for the tilting of the glass plates and the time devoted to its passage by the plates is dead time, i.e. time during which the state of the glass plates, i.e. the convex bending or hardening, does not undergo any development.